The present invention relates to an improved process for the production of trimethylsulfonium halides useful for producing oxiranes.
Trimethylsulfonium halides are useful precursors for epoxidation via sulfur ylides to form oxiranes. The use of aqueous trimethylsulfonium halides in phase transfer catalyst reactions with carbonyl compounds is known. See, for example, Merz et al. Angew. Chem. Internat. Edit., Vol. 12, pp. 845-6 (1973) and Hatch, J. Org. Chem. Vol 34, pp. 2133-2137 (1969). However, these aqueous solutions are formed by dissolving preformed trimethylsulfonium halides in water. The trimethylsulfonium halides are typically formed by reacting dimethyl sulfide and methyl halides in an organic polar solvent such as methanol or ethanol. The organic solvent must be completely removed before the trimethylsulfonium halide is added to the epoxidation mixture because the organic solvent will degrade the ylide.
It would therefore be advantageous to produce trimethylsulfonium halides directly in water so that the resulting aqueous solution could be used directly in the epoxidation process. Such a process would decrease the cost of making such intermediates because organic solvents would not be required, handling of the salt would be much easier and the need to purify the salt form organic impurities would be eliminated.